Indicator type switch assembly with peripheral cam follower motion transfer switch actuation means

ABSTRACT

A mechanism for operating a switch between first and second positions definitive of a rotatable member, such as an indicator pointer or shaft, being positioned on one side or the other of a selected point within a rotational range of substantially one revolution. Relatively rotatable paralled flat spring members are employed. A rotatable one of the flat spring members carries a cam follower, causing it to be deflected by a circumferentially positionable cam member berween one and the other of two positions, which deflection is imparted to a second flat spring which is constrained from rotation. The second spring deflection operates a standard fixed-mounted microswitch. Selected decision height annunciation for an altimeter indicator is exemplified.

United States Patent [191 Stockwell et al.

[5 1 INDICATOR TYPE SWITCH ASSEMBLY WITH PERIPHERAL CAM FOLLOWER MOTION TRANSFER SWITCH ACTUATION MEANS Inventors: Glade M. Stockwell; Benjamin B. Biderman, both of Cedar Rapids, Iowa Rockwell International Corporation, Dallas, Tex.

Filed: Dec. 26, 1973 Appl. No.: 428,167

Assignee:

[56] References Cited UNITED STATES PATENTS 4/1954 Raney et a1 200/153 LB X 12/1959 Smith 200/153 LB X 6/1960 Franck.;.. 200/153 LB X 5/1963 Spencer 200/56 R X [111 3,882,292 [451 May 6,1975

Primary Examiner-James R. Scott Attorney, Agent, or FirmRichard W. Anderson; Robert J. Crawford [57] ABSTRACT A mechanism for operating a switch between first and second positions definitive of a rotatable member, such as an indicator pointer or shaft, being positioned on one side or the other of a selected point within a rotational range of substantially one revolution. Relatively rotatable paralled flat spring members are employed. A rotatable one of the flat spring members carries a cam follower, causing it to be deflected by a circumferentially positionable cam member berween one and the other of two positions, which deflection is imparted to a second flat spring which is constrained from rotation. The second spring deflection operates a standard fixed-mounted microswitch. Selected decision height annunciation for an altimeter indicator is exemplified.

8 Claims, 7 Drawing Figures 1 39 ALTITUDE ,1 ALTITUDE SERVO INPUT PATENTED HAY 6 I975 SHEET MM 3 9 26 25 Firm 9 I I'd Illllllllllllllllllll 1111111114Iifilllllllllllllfiil ALTITUDE INPUT ALTITUDE SERVO POSITION FEEDBACK POT PATENTEUHAY 61975 3.882.292 SHEET UBDF 3 INDICATOR TYPE SWITCH ASSEMBLY WITH PERIPHERAL CAM FOLLOWER MOTION TRANSFER SWITCH ACTUATION MEANS This invention relates generally to switch activating mechanisms and more particularly to a means for operating a switch into one of two possible switch positions in accordance with the instant position of a rotatable member with respect to one side or the other of a preselected position within an overall rotational range approaching a full revolution.

As will be exampled herein, the present invention provides a novel and useful solution to the problem of radio altimeter indicator decision height annuciation.

Radio altimeter indicators are employed in the aircraft control art to provide a precise indication of altitude above runway for example, and comprise means for selecting some predetermined displayed altitude at and beneath which an annunciation is to be effected. The selected altitude reading is referred to in the art as a decision height, and indicators of this type might energize a warning lamp when this preselected decision height is reached and maintain the annuciation for all indicated altitudes beneath this decision height. Convefsely the systems provide that the annunciator lamp not be energized for any indicated altitude above the selected decision height.

Known means for accomplishing this generally described function have necessarily included somewhat elaborate printed circuit switch sectors with attendent sliding contacts such that a circuit is closed upon any indicated altitude equal to or less than the selected decision height, and open for all indicated altitudes above the selected decision height.

The combined requirement that the switch positions be initiated and held either side of selected decision height within the indicating range of the instrument has given rise to somewhat elaborate switching schemes. The indicator traverses substantially a full 360 scale. The selection of a decision height anywhere within this indicating range thus establishes nearly 720 of relative motion between the altimeter indicating pointer and that point of the indicator scale which is selected as the decision height altitude.

Thus, known switching systems for effecting decision height annunciation incorporate annular printed circuit Contact surfaces, which may be rotated relative to the shaft driving the altimeter pointer, together with further contacting means associated with the driven pointer per se to effect the switch connection and maintain the switch connection in the aforedescribed.

Sliding switch contacts with their attendance probability of failure and the printed circuit switch segments generally have given rise to complicated and necessarily expensive implementations.

Accordingly. the object of the present invention is to provide a mechanical switch activating mechanism for use in conjunction with an indicator, such as a radio altimeter indicator, whereby the decision height function is accomplished by actuating a stationary mounted switch (such as a microswitch) by a mechanical mechanism uniquely adaptable to solve the aforedescribed 720 relative rotation control problem.

A further described object of the present invention is the provision of a switching mechanism by means of which, for example, a decision height annunciation in a radio altimeter may be accomplished in a manner and reliable than switching means currently employed in the art.

A still further object of the present invention is the provision of a simplified switch activating mechanism which lends itself to construction from relatively inexpensive and common mechanical elements.

The present invention is featured in a motion transfer mechanism comprising a pair of parallel flat spring members one of which is fixed-cantilever mounted and constrained from rotation with respect to the indicator shaft and the other of which is cantelever mounted in a manner permitting selected rotation within its defined plane about an axis coincidence with the rotational axis of the indicator pointer. A cam follower member affixed to the free end of the selectively rotatable spring member cooperates with a camming surface means on a disc rotated with the indicator pointer .shaft such that the cam follower is caused to transfer from loaded engagement with one surface of the disc to the other surface thereof as the indicator pointer goes through a selected rotational segment corresponding to a selected decision height. Surface transfer of the cam follower member at the decision height is imparted as a deflection to the spring member carrying the follower, and this spring deflection is imparted through a simple motion transfer means to cause a like deflection of the fixed cantelever spring into operable engagement with a stationary mounted switch. The switch actuating method is thus realized by relative deflection of spring members as established by the cam follower riding on the upper or lower surface of the cam plate, with the point at which the cam follower transfer is effected being selectively established at any point within the indicating range of the instrument.

These and other objects of and features of the present invention will become apparent upon reading the following description with reference to the accompanying drawings in which:

FIG. 1 is a face view of a typical radar altimeter indicator with which the present invention may be incorporated;

FIG. 2 is a partial section view of a decision height switching mechanism in accordance with the present invention;

FIGS. 3a and 3b depict operation of a type of cam follower transfer mechanism which may be embodied in the present invention;

FIG. 4 is a functional diagram illustrating the general operating principle of the switching mechanism;

FIG. 5 depicts an embodiment of a pair of spring members as might be used in the invention; and

FIG. 6 is a partial mechanical view illustrating the relative mounting positions of the indicator pointer, decision height index, and cam actuating mechanism in accordance with the present invention.

The switch actuating mechanism of the present invention will be described as it might be incorporated into a radio altimeter indicator of the type including means for selective decision height annunciation. The general principle of the invention might be equally applicable for other usages since, in general, the principal might be applied to actuate a switch in accordance with the rotation of any rotatable member throughout substantially a complete revolution thereof wherein the rotational range might for one purpose or the other be selectively divided into two .complementary rotational segments and wherein it is desired that shaft rotation within a first of the segments causes a switch means to be in a first position thereof and rotation of the shaft within the second segment causes the switch to be in a second position thereof.

FIG. 1 illustrates the face of a typical radio altimeter wherein a pointer indicates experienced altitude on a circular scale 11. The typical indicator of FIG. 1 includes a manually adjustable control 13 for the purpose of selecting a decision height. Rotation of control 13 positions index 12 along the dial face to the selected decision height at and beneath which it is desired, for example, to illuminate an indicating lamp 14. I

The improved switch operating mechanism in accordance with the present invention is depicted in FIG. 2. Unlike'known decision height switching means which employ wafered switch surfaces. wiper arms, etc., the mechanism is a mechanical motion transmission means which operates stationary microswitch to accomplish the decision height switching function.

With reference to FIG. 2, indicator pointer 10 is afflxed to a drive shaft, 15 which is rotatable about a rotation axis 40. A servo system, for example, which responds to an'experienced altitude input analog may drive the pointer, in which case a signal proportional to experienced altitude 39 may be applied to an altitude servo 38 the output of which drives a servomotor 37 which through drive gear 36 pointer shaft 15 is driven bygear 36 such that the pointer 10 reads experienced altitude against the circular scale 11. A gear 43 driving potentiometer 41 develops a position feedback signal 42 to the altitude servo to complete the servo loop.

Pointer'shaft 15 is illustrated as being rotatable with respect to a fixed base member 31. A ring gear member 24 is retained in a rotatable relationship with respect to the fixed base member 31 by means of retaining plate 25. Plate 25 might be affixed to base member 31 as by exampled screw members 9. Ring gear member 24 is selectively rotatable with respect to the fixed base plate 31 by means of a driving gear 33 positioned by means of control knob 13 and a drive shaft 32 rotatably retained in the fixed base plate member 31 by means of retaining means 34. A first flat spring member 26 is fixed-mounted by means 27 to the retainer plate 25 and thus fixed-mounted with respect to the base plate 31. The flat spring member 26 is cantilever mounted in offset fashion and carries on the free end thereof a transversely extending actuating arm 28 which is slidably receivable through both the retaining plate 25 and the base plate 31 into operable engagement with the actuating button of a switch 29. Switch 29 might comprise, for example, a microswitch. In the depicted rest position, the actuating arm 28 might cooperate with the switch acuator button 30 such that the switch 29 is in a first defined position thereof.

A second flat spring member 20 is cantilever mounted by means 21 to the internal surface of the ring gear member 24. Flat spring member 20 extends such that its line of action transverses the pointer rotational axis and, by means of a transversally extending portion of the free end thereof, is affixed to a cam follower means 23. Cam follower means 23, as will further be described, operably engages a cam plate member 17.

Cam plate 17 as best depicted in FIGS. 3a and 3b is formed with inclined plane surface tab-like members 43 and 44 which might be comprised as integral out-ofplane inclined portions of the cam plate surfacetmutually oppositely directed). The cam plate 17 is affixed by means of a hub member 16 and locking means 18 for rotation with the pointer shaft 15 about the shaft rotational axis 40 and is oriented with the cam surface configuration on the same radial as that defined by pointer 10. For any selected radial position of the cam follower 23 it is seen from FIGS. 3a and 3b that rotation of the cam plate (and hence the indicator pointer 10) through a radial corresponding to the position coinciding with that of the cam follower member 23 causes a transfer of surface sliding engagement of cam follower 23 between one surface and the other of the cam plate 17, thus imparting a deflection of the mounting arm 22 which carries the cam follower 23. A downward deflection imposes a downward deflection of the spring member 20 which in turn is imparted, by means of a bushing member 19, as a like downward deflection of the fixed mounted spring member 26. Downward deflection of spring member 26 actuates switch 29 to a second position thereof. Thus, it may be seen that with the cam follower 23 riding on the upper depicted surface of cam plate 17 the switch 29 is in a first position and with the cam follower 23 riding on the lower surface of the cam plate 17 the switch is caused to be activated into the second position thereof. It is further seen that continued rotation of the pointer (and thus the cam plate) beyond the point at which the engagement transfer is effected, maintains the switch position established by the transfer. If, for example, the selected decision height as indicated by index member 12 is l00'feet, the cam follower member 23 is caused to ride the upper surface of the cam plate 17 (with switch 29 being maintained in a first position) until the shaft driving the altitude pointer rotates to the foot location at which time the mechanism causes the cam follower to transfer engagement to the lower surface of the cam plate. The resulting downward deflection of the spring member causes the switch 29 to be activated and maintained in the other position thereof.

FIG. 4 illustrates functionally the switching action effected by the mechanism. The upper spring member 20 is indicated functionally as being mounted at point 21, which mounting point is circumferentially positionable about the rotation axis 40 in accordance with the selected decision height setting. Since the free end of spring member 20 carries the cam follower member, deflection of spring member 20 is imparted through the bushing member 19 as a like deflection of the lower spring member 26 which is fixed mounted to the base plate.

The bushing member 19, by means of which deflection of the upper spring member is imparted to the lower spring member, is free to rotate and translate with respect to the pointer shaft 15 and may be slidably confined between appropriate through openings in the spring member surfaces. Relative rotation between the two spring member is thus permitted as different decision heights are selected with the line of action of each of the spring members passing through the rotational axis 40 of the indicator shaft 15. The cam follower 23 has decision height gear reference and the cam plate has pointer shaft reference. Since the cam follower is free to slide on either surface of the cam plate through approximately 360 rotation, a relative switch action control of nearly 720 is realized.

'FIG'. 5 depicts in plan view the manner in which the pair of flat spring members might be embodied. The rotatable flat spring 20 might be generally triangular in shape having first and second mounting means 21A and 21B on the internal surface of the ring gear member 24. The decision height index member 12 is affixed to the ring gear member 24 and adapted to over-ride the indicating'scale. FIG. 5 depicts the fix-mounted spring 26 as being affixed to the stationary retainer plate 25 by means of fasteners 27A and 278 with the switch actuating arm member 28 positioned on the free end and along the line of action of the spring 26 which passes through the rotational axis 40 of the pointer 10. in the embodiment depicted in FIG. 5, each of the spring members is formed with an appropriate throughhole providing clearance for unimpeded deflection of the fix-mounted' spring member 26 and unimpeded rotation and deflection of the rotatably mounted springv member 20.

FIG. 6 illustrates the fixed relationship between the camming surfaces 43 and 44 formed on cam plate 17 and the indicator pointer such that both the cam surface arrangement and the pointer rotate with the driven indicator shaft about the rotational axis 40.

Obviously numerous spring shapes might be incorporated without departing from the principle of the invention.

In a preferred embodiment, the rest position of the rotatable flat spring member might be chosen such that the cam follower carried by the free end thereof is in neutral position with respect to the camming surfaces on cam plate 17 (as depicted in FIG. 2). This de sign expedient advantageously provides a spring loaded engagement of the cam follower member 23 with respect to one surface or the other of the cam plate 17 once the cam plate rotates past the neutral position.

The present invention is thus seen to provide a purely mechanical arrangement by means of which a decision height annunciating switch may be appropriately activated between first and second positions thereof. No sliding contacts are needed, and the complication and expense of utilizing wafer contact segments, pendant wire interconnections, etc., are obviated. The present invention provides a positive mechanical actuating mechanism permitting the use of a simple microswitch to accomplish the desired switching function. The mechanism may be constructed from simple, inexpensive mechanical elements.

Although the present invention has been described with respect to a particular embodiment thereof, it is realized that numerous mechanical mounting expedients might be employed without departing from the invention as defined in the appended claims.

1 claim:

1. A switching mechanism responsive to rotation of a rotatable member from one preselected rotational segment to an adjacent complementary segment thereof comprising: means for mounting said rotatable member for rotation about an axis normal to a mounting base member, an arcuate plate member, means for mounting said arcuate plate member for rotation about the axis of said rotatable member and in concert therewith, camming surface means carried by said arcuate plate member at a point on the circumference thereof corresponding to a reference point on said rotatable member, cam follower means being selectively positionable about the circumference of and in spring loaded engagement with said arcuate plate member, said cam follower means, when operably engaged with said camming surface means, effecting a transfer of engagement of said cam follower means from one planar surface of said arcuate plate member to the opposite planar surface thereof to effect a predetermined translation of said cam follower means transverse the plane defined by said arcuate plate member, switching means fixed-mounted with respect to said mounting base member. motion transfer means connected to said cam follower means and said switch member, said motion transfer means being responsive to said cam follower engagement transfer to activate said switching means from one to the other of two possible positions thereof.

2. Means as defined in claim 1 wherein said camming surface means comprises first and second inclined plane surfaces formed as respective oppositely directed tabs integrally formed as out-of-plane portions of said arcuate plate member and collectively defining a radially inwardly extending through-slot in the periphery of said arcuate plate member.

3. Means as defined in claim 1- wherein said cam follower comprises guide means engagable with the respective surfaces of said arcuate plate member and, upon camming engagement with one of said arcuate plate member inclined plane surfaces, being transferrable from surface engagement with one side of said arcuate plate member to the other side of said arcuate plate member.

4. The mechanism as defined in claim 1 wherein said cam follower is affixed to the free end of a first cantilever mounted planar spring member, the longitudinal axis of said first spring member transversing the rotational axis of said rotatable member, said first spring member being mounted on the circumference of an annular mounting means, means for selective rotating said annular mounting means about the rotational axis of said rotatable member, said first spring member lying in and defining a plane substantially normal to the rotational axis of said rotatable member, said first spring member effecting a predetermined spring loaded engagement of said cam follower with respect to surfaces of said arcuate plate member upon engagement with either surface of said plate member, a second cantilever mounted planar spring member, said second spring member lying in and defining a plane substantially parallel to and space-separated from that defined by said first spring member, said second spring member being constrained from rotation with respect of the rotational axis of said rotatable member and with the longitudinal axis thereof transversing said rotational axis, motion linkage means coacting with said first and second spring members to impart deflection of said first spring member with respect to the mounted end thereof as a substantially like deflection of the free end of said second spring member, and said switching means including an actuating member in driven engagement with the deflectable free end of said second spring member to be activated thereby.

5. The mechanism as defined in claim 4 comprising a further index means mounted for selected rotation with respect to the rotational axis of said rotatable member and on a radial common to that of said cam follower means, said further index means providing an indication of that rotational position of said rotatable member at which said aforedefined cam follower engagement transfer is effected.

6. The mechanism as defined in claim 4 wherein said motion linkage means between said first and second planar spring members comprises a bushing member retained between respective surfaces of said first and second planar spring members and rotatable with respect to at least one of said spring members, whereby relatively rotation between said first and second spring members is enabled and deflection of said first spring member is imparted as a like deflection of said second spring member.

7. Apparatus for activating a switch from a first position thereof to a second position thereof at a selected rotation position of a shaft within a range of rotation substantially equal to and less than a full revolution; comprising means for mounting said shaft for rotation with respect to a mounting base member, a first cantilever mounted flat spring member lying in and defining a plane substantially normal to the rotational axis of said shaft and having a deflection line of action intersecting the rotational axis of said shaft. said first spring member being fixed-mounted withrespect to said base member and constrained from rotation with respect to said shaft. a second cantilever mounted flat spring member lying in and defining a plane substantially parallel that of said first spring member and having the mounted end thereof affixed to a ring mounting means, means for rotatably mounting said ring mounting means with respect to said base member for rotation independent of that of said rotatable shaft and about a rotational axis coincidence with that of said shaft, the.

deflection line of action of saidsecond spring member transversing the rotational axis of said shaft, a cam follower affixed to the free end of said second spring member, a circular cam plate fixed-mounted transverse of said shaft and rotatable with said shaft, said cam plate having formed-therein at a selected radial on the periphery thereof a notch defined by adjacent opposi'tely directed out-of-plane tabs, said cam follower means upon engagement with said tabs being caused to transfer sliding engagement thereof from one surface of said cam plate to the other surface thereof, motion transfer means engaging each of said spring members member freely extends. 

1. A switching mechanism responsive to rotation of a rotatable member from one preselected rotational segment to an adjacent complementary segment thereof comprising: means for mounting said rotatable member for rotation about an axis normal to a mounting base member, an arcuate plate member, means for mounting said arcuate plate member for rotation about the axis of said rotatable member and in concert therewith, camming surface means carried by said arcuate plate member at a point on the circumference thereof corresponding to a reference point on said rotatable member, cam follower means being selectively positionable about the circumference of and in spring loaded engagement with said arcuate plate member, said cam follower means, when operably engaged with said camming surface means, effecting a transfer of engagement of said cam follower means from one planar surface of said arcuate plate member to the opposite planar surface thereof to effect a predetermined translation of said cam follower means transverse the plane defined by said arcuate plate member, switching means fixedmounted with respect to said mounting base member, motion transfer means connected to said cam follower means and said switch member, said motion transfer means being responsive to said cam follower engagement transfer to activate said switching means from one to the other of two possible positions thereof.
 2. Means as defined in claim 1 wherein said camming surface means comprises first and second inclined plane surfaces formed as respective oppositely directed tabs integrally formed as out-of-plane portions of said arcuate plate member and collectively defining a radially inwardly extending through-slot in the periphery of said arcuate plate member.
 3. Means as defined in claim 1 wherein said cam follower comprises guide means engagable with the respective surfaces of said arcuate plate member and, Upon camming engagement with one of said arcuate plate member inclined plane surfaces, being transferrable from surface engagement with one side of said arcuate plate member to the other side of said arcuate plate member.
 4. The mechanism as defined in claim 1 wherein said cam follower is affixed to the free end of a first cantilever mounted planar spring member, the longitudinal axis of said first spring member transversing the rotational axis of said rotatable member, said first spring member being mounted on the circumference of an annular mounting means, means for selective rotating said annular mounting means about the rotational axis of said rotatable member, said first spring member lying in and defining a plane substantially normal to the rotational axis of said rotatable member, said first spring member effecting a predetermined spring loaded engagement of said cam follower with respect to surfaces of said arcuate plate member upon engagement with either surface of said plate member, a second cantilever mounted planar spring member, said second spring member lying in and defining a plane substantially parallel to and space-separated from that defined by said first spring member, said second spring member being constrained from rotation with respect of the rotational axis of said rotatable member and with the longitudinal axis thereof transversing said rotational axis, motion linkage means coacting with said first and second spring members to impart deflection of said first spring member with respect to the mounted end thereof as a substantially like deflection of the free end of said second spring member, and said switching means including an actuating member in driven engagement with the deflectable free end of said second spring member to be activated thereby.
 5. The mechanism as defined in claim 4 comprising a further index means mounted for selected rotation with respect to the rotational axis of said rotatable member and on a radial common to that of said cam follower means, said further index means providing an indication of that rotational position of said rotatable member at which said aforedefined cam follower engagement transfer is effected.
 6. The mechanism as defined in claim 4 wherein said motion linkage means between said first and second planar spring members comprises a bushing member retained between respective surfaces of said first and second planar spring members and rotatable with respect to at least one of said spring members, whereby relatively rotation between said first and second spring members is enabled and deflection of said first spring member is imparted as a like deflection of said second spring member.
 7. Apparatus for activating a switch from a first position thereof to a second position thereof at a selected rotation position of a shaft within a range of rotation substantially equal to and less than a full revolution; comprising means for mounting said shaft for rotation with respect to a mounting base member, a first cantilever mounted flat spring member lying in and defining a plane substantially normal to the rotational axis of said shaft and having a deflection line of action intersecting the rotational axis of said shaft, said first spring member being fixed-mounted with respect to said base member and constrained from rotation with respect to said shaft, a second cantilever mounted flat spring member lying in and defining a plane substantially parallel that of said first spring member and having the mounted end thereof affixed to a ring mounting means, means for rotatably mounting said ring mounting means with respect to said base member for rotation independent of that of said rotatable shaft and about a rotational axis coincidence with that of said shaft, the deflection line of action of said second spring member transversing the rotational axis of said shaft, a cam follower affixed to the free end of said second spring member, a circular cam plate fixed-mounted transverse of said shaft and rotatable with said shaft, sAid cam plate having formed therein at a selected radial on the periphery thereof a notch defined by adjacent oppositely directed out-of-plane tabs, said cam follower means upon engagement with said tabs being caused to transfer sliding engagement thereof from one surface of said cam plate to the other surface thereof, motion transfer means engaging each of said spring members and imparting deflection of said first spring member as a like deflection of said second spring member, and said switch having an actuating member engaging said second spring member and being responsive to deflection of said second spring member to be activated.
 8. Apparatus as defined in claim 7 wherein each of said spring members are formed with openings through the surfaces thereof through which said rotatable shaft member freely extends. 